As a vehicle is operated on a road, irregularities in the road surface induce movements of the vehicle's tires. These movements in turn are transmitted through the vehicle suspension to the vehicle interior. The damper component of the suspension is designed, among other things, to manage movements of the vehicle body and suspension mass, as well as the transmissibility of road excitation to body motion. Equipment designed to measure and test damper configurations are known as shock press machines and are used to quantify dampers for their role in these functions.
In addition, there are irregularities in rotating components located at corners of vehicles, such as imbalance, out of roundness and eccentricities in tires, wheels and brake rotors. These irregularities also result in internal vehicular forces which produce movements that are transmitted to the vehicle interiors. These movements are most notable on smooth roads for which an external source of the movement is not apparent and are referred to collectively as “smooth road shake.” Current dampers are usually not effective in reducing the transmissibility of these irregular movements. These dampers are typically evaluated and developed on conventional damper measurement systems which are not designed to measure the dampers under conditions representative of operation on smooth roads.
Conventional shock press machines are designed to exercise and measure dampers at relatively large displacements, e.g., several mm and velocities, e.g., 1 m/sec. Control movement and measuring forces and velocities at very small displacements in the range of 0.050 to 2 mm (peak-to-peak), as are typical of operation on smooth roads, is an undertaking not currently practiced. Accordingly, in order to effectively design dampers, such as the dampers for vehicle suspensions disclosed in co-pending and co-assigned U.S. Patent Application titled “Dual Stage Dampers For Vehicle Suspension” (Attorney Docket No. GP-304924), incorporated herein in its entirety by reference, new methods for testing damper designs are needed.